The present invention relates to an electrochemical cell and, more particularly, to a primary electrochemical cell including a hold-down unit for securing and preventing movement of a physically large battery stack of the cell.
Primary electrochemical cells are commonly available in a large assortment of sizes and shapes. One type of primary electrochemical cell which has been particularly successful, especially for high-current drain, low-temperature applications, is a so-called prismatic cell. Such a cell is generally described in U.S. Pat. No. 4,086,397, in the names of Franz Goebel and Nikola Marincic, and includes a physically large battery stack enclosed together with an electrolytic solution within a large, generally-rectangular metal housing. The battery stack as used within the cell comprises a large number of generally-rectangular cell components including a plurality of anodes, carbon cathode current collector electrodes, and insulative separators between the anodes and the carbon cathode current collector electrodes. Each anode generally comprises a large rectangular sheet of an oxidizable alkali metal, such as lithium, physically impressed into a supporting (e.g., nickel) grid, and each of the carbon cathode current collector electrodes comprises an aggregation of porous, semi-rigid carbon globules or conglomerates physically impressed into a metal (e.g., nickel) current collector grid. Each of the anodes and carbon cathode current collector electrodes further has a narrow rail around the periphery thereof and a tab connected to the rail for facilitating physical and electrical connection of the associated electrode to a corresponding terminal assembly. A common and preferred electrolytic solution employed in the cell as described above is a cathodelectrolyte solution comprising a reducible soluble cathode such as thionyl chloride and an electrolyte solute such as lithium tetrachloroaluminate dissolved in the thionyl chloride.
By the appropriate selection of the battery cell components, a cell as described above can be constructed to have any one of several possible sizes and energy configurations. A typical cell can, for example, have exterior dimensions of approximately 18 inch (height).times.13 inch (width).times.10 inch (depth), a weight of 156 pounds, an ampere-hour capacity rating of 10,000 ampere-hours, and a nominal discharge current of 40 amperes.
The cell as described hereinabove is generally operated in an undisturbed, vertical, upright position. However, in actual practice, it is possible for the cell to be moved or transported from one place to another, to be turned upside down or on its side, and/or to be exposed to vibration, shock, or other physically abusive or unsettling conditions. In any of these situations, it is possible for the battery stack or components thereof to be disturbed or displaced from their initial or operating position. If the disturbance of the battery stack or components thereof is substantial, undesirable short-circuit conditions can occur which, considering the very high-energy, high-current characteristics of the cell, can lead to severe physical damage to the cell.